A large number of embodiments are known for the design configuration and construction of electrical drives for vehicles, in particular hybrid drives for vehicles. Embodiments for driving a front wheel shaft of a vehicle are in this case preferably designed using a transverse shaft structure. The shaft drive unit in this case comprises an electrical drive machine which can be operated as an electric motor in the traction mode and is connected to the wheel shaft via a transmission unit. The power for operating the electrical drive machine is provided via a power supply system which, depending on the choice of energy source, may have various configurations. Referring to FIG. 1, there is seen a power system in the form of an internal combustion engine 100 mechanically and electrically coupled to an electrical machine 1 according to the present invention via a mechanical connection 105, and a fuel cell 110 electrically connected to the electrical machine 1 via electrical connection 115. It is in this case feasible for the power source to be in the form of an internal combustion engine an energy storage unit or what is referred to as a fuel cell. In each case, means are required for transmitting the power to the electrical drive machine. In order to control the electrical drive machine, it has at least one converter unit associated with it, which converter units determine the magnitude of the torque and rotation speed which can be delivered from the rotor of the electrical drive machine.
In embodiments with a transverse shaft structure, the rotor of the electrical drive machine is connected in a rotationally fixed manner to an input (when considered in the power flow direction in the traction mode) of the transmission unit. The output from the transmission unit is coupled in a rotationally fixed manner to the wheel shaft.
The expression wheel shaft in this case relates to the coupling to the wheels, which are connected in a rotationally fixed manner to that shaft, so that there is no relative movement between the wheels and the wheel shaft. However, with regard to power transmission, the wheel shaft acts as an input drive shaft for the wheels, which are coupled in a rotationally fixed manner to it. However, the expression wheel shaft is used in the following text. The input drive to and the output drive from the transmission unit as well as the rotor of the electrical drive machine and the wheel shaft are arranged coaxially with respect to one another. Specifically, this means that, for example, the rotor of the electrical machine and the input to drive to the transmission unit enclose the wheel shaft.
At least one converter unit is provided in order to drive the electrical machine, and can be arranged at any desired distance from the electrical machine, within the vehicle. The coupling is in this case provided via appropriately shielded electrical cables. In order to ensure reliable operation, cooling water lines must then also be provided, in addition to the electrical cables, between the converter units, in order to provide a separate cooling circuit. Owing to the physical separation, the line and cable routing required for this purpose is generally also very expensive and complicated. Furthermore, long cable runs also mean an increase in the frequency-dependent effects of electrical, magnetic or electromagnetic fields on the environment, in particular on living beings and technical systems. This effect, which can be summarized by the expression electromagnetic compatibility, is defined by numerous national and international standards. Appropriate shielding must be provided in order to comply with the limit values specified in this case. However, this is independent of the line and cable routing and may differ to a very major extent from one particular application to another, in which case the EMC shielding must be implemented as an additional feature, with different boundary conditions, for each application. A further major disadvantage of these embodiments is that the reliability of the overall system decreases as the length of the cooling water lines and/or the electrical connecting cables increases, and this is due, inter alia, to the larger area on which insulation damage can occur on electrical cables, and over which leakages can occur in the cooling circuit.
By analogy, this statement also applies to the association of braking resistor units with the electrical drive machine, with these braking resistor units converting the electrical power to thermal energy in the generator mode. In this case as well, there is a requirement for these braking resistor units to be integrated in the drive system in an optimum manner. Since they are electrically coupled to the electrical machine, the same problems as those which occur in the arrangement of the converter units exist in embodiments where considerable physical distances are involved.